1. Field of the Invention:
This invention relates to photographic lens barrel and more particularly to a lens barrel having input-and-output means for electrical signal exchange with a camera body and means which is arranged within the body of the lens barrel to be controlled and driven by an electrical signal.
2. Description of the Prior Art:
The lens barrel to which this invention relates is of the type suitable for use as an interchangeable lens arranged to be freely attachable to and detachable from a camera body.
The conventional mounting arrangements for interchangeable lens barrels include: the type wherein the entire lens barrel assembly is rotated when attaching it to the camera; the spigot type in which the lens barrel is attached to the camera by a bayonet tightening ring provided on the periphery of one end of the lens barrel; and the latest type which has been developed by the present applicants and covered by and described in U.S. Pat. Nos. 4,247,190, 4,230,403, 4,281,916, 4,317,627 and 4,302,077.
The lens barrel of this latest type principally comprises, as disclosed in U.S. Pat. No. 4,230,403, an adapter shell 8 which is arranged to be non-rotatably secured to a camera body and a lens body which consists of a lens barrel 1 (or a main support tube 1) and a ring 4 arranged to be rotatable around an optical axis relative to the adapter shell 8. The lens body has a photo-taking lens and a diaphragm attached thereto.
In the above-stated latest type lens barrel assembly, a signal member which is provided for exposure control between the camera and the interchangeable lens is attached to the adapter shell. The signal member is arranged to be always kept in a predetermined position when the lens barrel is attached and detached to and from the camera, so that the signal member can be always smoothly interlinked with a corresponding member arranged on the camera body.
A recent conspicuous technological advance in cameras involves the advent of automatic focusing devices. These automatic focusing devices include a first type which is arranged to guide reflected light coming from a photographing object via a photo-taking lens to a distance measuring element disposed on the side of a camera body and to control the shift of the photographic lens on the basis of a signal produced by the distance measuring element; and a second type having a distance measuring element, a distance measurement control circuit and photographic lens driving means all arranged within the interchangeable lens barrel.
The first type necessitates use of signal transmission device for exchange of electrical signals between the camera and the interchangeable lens barrel.
The second type also requires a signal transmission device for signal transmission between the camera and the lens barrel when the light quantity of a flash device is to be controlled by sending a distance measurement signal from the lens barrel to the camera body.
The recent technological advance in camera systems also has resulted in the application of electronics for improvement in the accuracy of electrical signal control between the camera body and the lens barrel. Such improvement includes provision of a stepping motor for aperture control; electrification of the photographic lens by adoption of an automatic focusing device; and an electrical zooming arrangement for a zoom lens.
The application of electronics to camera systems also has come to necessitate use of a device for electrical signal exchange between the camera body and the lens barrel. However, the electrical signal exchange device is greatly dependent on the type of the above-stated mounting arrangement of the interchangeable lens barrel.
In the type wherein the entire lens assembly may be rotated during mounting, a bayonet mount is provided at the end of the lens barrel and the bayonet mount is engaged with a corresponding bayonet mount provided on the camera body side with the lens barrel being attached to the camera by turning the whole lens barrel around the optical axis as mentioned in the foregoing. For this type, electrical signal receiving-and-producing means can be arranged without much difficulty by providing contact pins on the mount surface of the lens barrel and that of the camera body in a manner as disclosed in U.S. Pat. No. 4,357,089.
However, in the case of the lens barrel which is provided with the above-stated new type mounting device, the adapter shell and the lens body are arranged to be rotatable relative to each other and it is difficult to use the conventionally known electrical signal transmission device for the lens barrel because in the new type mounting device, the adapter shell which is arranged to engage the mounting surface of the bayonet mount of the camera body is rotatable relative to the lens body and, with a diaphragm, a stepping motor for driving the diaphragm, etc. arranged in the lens body, the signal receiving-and-producing means (or input-and-output means) such as the contact pins provided on the adapter shell must be provided with some arrangement for electrical signal transmission between the signal receiving-and-producing means and the motor or the like and a motor control circuit.
Lens barrels generally have a very tight structural arrangement without leaving vacant spaces therein to meet the requirement of the market for reduction in size and weight. Use of some wiring arrangement such as the one disclosed by Japanese Utility Model Publication No. SHO 52-60833 is difficult in view of the requirement for reduction in size and weight. Therefore, the interchangeable lens barrel provided with the above-stated new type mounting device has presented a problem with respect to the electrical signal transmission arrangement.
Further, with regard to the electrical signal exchange arrangement of a photographic lens barrel and particularly that of an interchangeable lens barrel, some problems still ramain unsolved. For example, in connection with the above-stated applications of electronics to a lens barrel, the unsolved problems include simplification of the electrical signal transmission arrangement within the lens barrel and obtaining sufficient reliability of the signal transmission arrangement. Another problem resides in achieving electrical signal transmission between a fixed shell and an operation member which is disposed on the outer side of the fixed shell and is arranged to be movable either around an optical axis or linearly along the optical axis. It has been known to provide the operation member with an electrical unit consisting of electrical elements and electrical circuit substrate; to arrange an input-and-output device (such as electrical signal pins and the like) at one end of the fixed shell facing the camera; and to effect electrical signal transmission between the electric unit and the input-and-output device via the fixed shell. For such an arrangement, signal transmission means consisting of an electrical conductor plate and a sliding brush has been considered usable. However, it has been a shortcoming of the signal transmission means that the reliability of electrical signal transmission cannot be ensured because of insufficient conduction resulting from imperfect contact due to wear of the sliding brush, insufficient contact pressure and dust. The conventional signal transmission means thus has posed a problem in terms of reliability and quality.